Fluoropolymer filtration membranes are well known, as described in US patents such as U.S. Pat. Nos. 6,013,688 and 6,110,309. Fluoropolymers, such as polyvinylidene fluoride (PVDF) are very chemically and biologically inert and have outstanding mechanical properties. They are resistant to oxidizing environments, such as chlorine and ozone, which are widely used in the sterilization of water. PVDF membranes are also highly resistant to attack by most mineral and organic acids, aliphatic and aromatic hydrocarbons, alcohols, and halogenated solvents. Fluoropolymers in general, and especially PVDF, is resistant to sterilization by, for example, steam, chemicals, UV radiation, irradiation, and ozone.
U.S. Pat. No. 3,864,124 describe the use of polytetrafluorethylene (PTFE) to immobilize a non-fiberizing material.
U.S. Pat. Nos. 5,019,311, 5,147,722 and 5,331,037 describe an extrusion process to produce a porous structure containing interactive particles bound together by a polymer binder. The porous structure is described as a “continuous web matrix”, or “forced point bonds”. The solid composite article is useful as a high performance water filter, such as in a carbon block filter. Thermoplastic binders listed for use in the process include polyvinyl fluoride as the only fluoropolymer, with examples of polyethylene and polyamide 11. Polyvinyl fluoride is difficult to process, as it is not thermoplastic.
US 2010-0304270 describes the use of an aqueous composition containing a high molecular weight aqueous fluoropolymer binder and a powdery material (such as carbon) to produce a porous solid material in which the particles are bound together only at specific discrete points to produce interconnectivity. The particles are bound together in a continuous web, while leaving the majority of each particle exposed to fluids passing over them. The binder level used is 0.5 to 25%, preferably 0.5-15% and most preferably from 1-10%.
It has now surprisingly been found that high molecular weight fluoropolymer and polyamide binders can be used to bind interactive particles and/or fibers together in such a manner as to create interconnectivity of the particles and/or fibers. The bound particles or fibers can be formed into articles for the separation of materials dissolved or suspended in fluids. The porous solid separation articles are especially useful for the removal of contaminants from potable water; the separation of contaminants from liquid or gaseous industrial streams; the capture and recovery of small molecules from fluid streams, such as biological and pharmaceutically active moieties, and precious metals, and the performance of specific chemical reactions, such as through catalysis. Depending on the type of activity of the interactive particles, the particles may separate the dissolved or suspended materials by chemical reaction, physical entrapment, electrical (charge or ionic) attraction, or similar means.